This tutorial will teach you how make your own creamy, skin-nourishing milk soap!
Pretty much any cold process soap recipe that calls for water, can be made with milk, or a milk substitute instead. You just need to take a little different approach to make sure you don’t scorch the milk or overheat your soap.
If you’d like more in-depth cold process soap making information, tips on coloring soaps naturally and lots of palm-free recipes, check out my complete Handmade Natural Soaps eBook Collection.
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Things to know before you start:
- Lye is a requirement when making homemade soap. It seems scary and dangerous, but I assure you – if you can safely and responsibly work with strong chemicals such as bleach and ammonia, then you can handle lye. (Read more about that topic HERE.)
- There are two types of lye: sodium hydroxide (for solid bars of soap) and potassium hydroxide (for liquid soaps.) I buy and recommend Essential Depot’s food grade lye from Amazon.
- Safety equipment is a must. This includes: goggles to protect your eyes, long sleeves in case of accidental splashes, and gloves to keep your hands from coming in contact with lye solution or raw soap batter. When you first mix lye into water, milk, or other liquid, it can give off strong fumes. Work in a well ventilated area and try not to directly breathe them in. I work in my kitchen sink to catch spills and because it has a window right over it for fresh air. If you have chronic breathing issues or feel concerned about the fumes, consider using a full face ventilation mask. (Those little pollen or dust masks won’t cut it.)
- All measurements are by weight, not volume. You need an accurate digital scale to make soap. Guessing or eyeballing could make you end up with soap that’s too slimy from not enough lye or too harsh from too much lye. (Check my Amazon shop to see the scale & other equipment I use.)
- This is how I make milk soap. It’s not the one and only way – there are other methods. If you see someone on the internet elsewhere doing things differently, it doesn’t mean that they or I are wrong in our method. The great thing about soap making is that there’s tons of room for individuality and different approaches!
For this tutorial, we’re going to use the following recipe:
Basic Milk Soap Recipe
Liquid & Lye Portion:
- 9 oz (255 g) milk
- 4.3 oz (122 g) lye (sodium hydroxide)
- optional: 1 1/2 tsp sodium lactate (to help harden soap)
Oils Portion (31 ounces total):
- 22 oz (624 g) olive oil (71%)
- 8 oz (227 g) coconut oil (26%)
- 1 oz (28 g) castor oil (3%)
You can source oils from a variety of places including a local grocery store or online vendors.
Milk type can be: cow, goat, coconut, rice, almond, and so forth. I use whole milk – sometimes raw and sometimes pasteurized, since that’s what we drink, but you can use lower fat versions as well. When using milk substitutes, the less additives, the better.
Note: High olive oil soaps like this one sometimes take a little longer to set up and cure. Olive oil is a soft/hard oil. It starts off causing the soap to be on the softer side, but once it cures for an extended time, the bar will grow very hard, yet extremely gentle on your skin. You can reduce the amount of milk by an ounce or two, if you’d like to speed up the process. Reducing liquid is also helpful when using silicone molds.
Step 1: If you use a different recipe (or even one from this site), run it through a lye calculator to make sure the lye and oil amounts were typed in correctly. I like the ones at Majestic Mountain Sage or Soapee best. For more detail on using lye calculators, read up on my post How To Make Any Soap Recipe Palm Free.
Step 2: In order to keep the sugars in milk from scorching, it needs to be icy cold or even frozen, before adding lye. To do this, freeze your milk in ice cube trays or put it in the freezer until slushy.
Step 3: Assemble all of the ingredients, utensils, and safety gear that you’ll need. It’s helpful to jot yourself a step-by-step checklist, to refer to as you go.
Step 4: Prepare your mold. This recipe (31 ounces of oil) fits in any of the following molds:
- Crafter’s Choice Silicone Loaf Mold 1501 (I use this mold a ton, it’s a favorite!)
- Silicone Column Mold (from BrambleBerry) – when using silicone, decrease the amount of liquid to 8 ounces and allow to stay in the mold a few extra days. You can also add 1 1/2 teaspoons sodium lactate (a natural salt solution from corn or beets) to the lye solution after the lye is completely dissolved, to make the soap batter firm up faster in the mold.
- 12 Bar Silicone Mold (also from BrambleBerry) – the recipe will fill about nine of the cavities. Same suggestions for silicone molds above, applies to this mold as well.
- Wooden Mold – I use one homemade by my husband. Its inner dimensions are 8″ x 3.5″ x 3.5″. Wooden molds should always be lined with parchment or freezer paper.
Step 5: Pull out the milk you plan to use in your soap recipe. If it’s in the form of ice cubes or chilled/slushy liquid, weigh out the amount you need, into a heat proof plastic pitcher. If you already weighed and have a solidly frozen amount of milk in your pitcher, then move on to step 6.
Step 6: Wearing gloves and goggles, weigh out the lye (sodium hydroxide). You must use a digital scale for this part.
Step 7: Pour the lye into your milk, just a sprinkle at a time. If your milk is frozen solid, you might need to add a tiny splash of water first to get it started, but the reaction of the lye with milk will quickly start melting everything, as you stir.
Add the lye slowly, stirring constantly. It will take several minutes to do this – don’t rush this part. Make sure every bit of lye is dissolved. The milk might turn a bright yellow and smell a little weird. That’s okay and perfectly normal.
Once the lye is fully dissolved (check that there’s no grainy bits on the bottom of the container), stir in 1 1/2 teaspoons sodium lactate if using.
Set the lye and milk mixture aside while you measure out the oil portion of your recipe.
Step 8: In a stainless steel, heavy duty plastic, or enamel lined container/pot, combine the olive, coconut, and castor oil. (Remember, all measurements are by weight.) If it’s too solid to combine, briefly melt the coconut oil in a small saucepan until softened or liquified. Soap oils should be around 90 to 100 degrees F.
Step 9: Drizzle the lye mixture into the oils. Using a stick blender (immersion blender), like THIS ONE, begin stirring the oil and lye solution together. Alternate stirring with the motor on and then off. Don’t run the stick blender the entire time or you risk lots of air bubbles and possibly a too-fast or false trace.
Pulse the stick blender only a few seconds at a time, then stop and stir with the motor off. Repeat until you reach trace, which may take about four or five minutes. (“Trace” means that soap batter is thick enough to hold an outline, or “tracing” when drizzled across the surface of itself.)
The following photo is what trace looks like:
Once trace is reached, you can stir in essential oils for scent, colorants such as clays or botanicals, or add-ins like oatmeal, honey, and so forth.
Step 10: Working quickly, pour the fresh soap batter into your mold. When making soaps without milk, I often cover with a blanket and allow to sit undisturbed for around 24 hours. This allows the soap to go through gel phase. “Gel phase” means that the soap has heated up higher in the mold, than when you poured it. Gel phase brings out colorants and makes them “pop”, and some people like the final texture of the soap better.
However, milk soap that goes through gel phase may be darker and browner than milk soap that is not allowed to go through gel phase. If you’d like a whiter soap, place your mold in the refrigerator or freezer, for around 24 hours. This prevents gel phase. Once you’re removed it from the cold, it will still be soft and will need another 24 to 48 hours in the mold at room temperature.
The photo below shows two freshly unmolded bars of soap, both made using the same recipe as listed here and with whole cow’s milk. The soap on the left sat in a mold, uncovered and at room temperature for 24 hours while the soap on the right was immediately placed in the freezer for 24 hours. Both soaps work great, the difference in the final, cured bar is mainly cosmetic.
With milk soap, remember: mold at room temperature = browner soap; mold in freezer = whiter soap. (Note: Over cure time, the brown bar lightened up a few shades, and the white bar turned more ivory toned.)
Step 11: Unmold your soap and slice into bars. Allow the bars to cure in the open air, on a sheet of wax or parchment paper, for at least four to six weeks, rotating occasionally. Because of the higher amount of olive oil in this soap recipe, the longer you let it cure, the harder the final bar will be.
Step 12: Enjoy your soap! It makes a great gift for family and friends too!
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